1. Field of the Invention
The invention relates to apparatus for controlling the spraying or other dissemination of a fluid from a reservoir, through the sequential opening and closing of a plurality of spray valves, and control of the flow rate and pattern of flow from each spray valve.
2. Description of the Prior Art
There are numerous applications in which it is necessary to continuously control the dissemination of a fluid from a reservoir, through control of the sequence, rate and direction of flow from a number of spray valves. There are, for example, numerous agricultural and contracting operations in which tank trucks are used to selectively spray a liquid along particular paths where the liquid may produce some beneficial result. Other vehicles, for example crop dusting planes and fire fighting planes, need an accurate system for control of fluid dissemination to insure effectiveness and avoid waste.
Selective control of the sequence, rate and pattern of flow from a plurality of spray valves is often necessary to minimize wastage of valuable fluid, or to minimize the time required to carry out the operation.
It is desirable that the sequence of opening and closing of the individual spray valves be easily controllable by a single operator from a central location, as in the cab of a spray truck.
Since such operations are often conducted in a sandy or dusty environment, it is also desirable to utilize individual spray valves so designed and fabricated as to minimize the possibility of malfunctions resulting from jamming of the valve mechanism by sand or dust.
It is, of course, also desirable to utilize a valve of simple design and few parts, so as to minimize the costs of construction, operations and repair.
One valve which has been previously used in tank truck spraying operations is that disclosed in the patent of Sons (U.S. Pat. No. 3,552,658), and was invented by one of the present applicants. This patent discloses a spray valve having a ram (FIG. 1, No. 98) which is moved by the application of compressed air so as to seal against an O-ring in the lower valve body member, shutting of the valve (Col. 4, lines 63-71).
In the Sons patent the ram of the spray valve is guided in the base of the valve head between two O-rings seated in the interior wall of the bore (Col. 3, lines 46-49; FIG. 1, Nos. 90, 92 and 100). The O-rings serve to prevent the control air pressure from leaking past the ram, down the bore. In application of this valve in spraying operations applicants have observed that the valve has a marked tendency to malfunction when used in a sandy environment, in that sand particles which find their way into the spray fluid frequently become wedged in the space between the outer wall of the ram and the interior wall of the valve head bore, particularly in the region of the two O-rings, thus jamming the ram mechanism. It will also be apparent that the valve of the Sons patent has more parts, and is accordingly more expensive to fabricate, than the valve described hereinbelow.
Applicants are aware of a type of valve presently manufactured by more than one manufacturer, not disclosed in any patent known to applicants, which is similar in some respects to the spray valve described hereinbelow. In this valve a rubber seating member is normally (when the valve is closed) held against a metal seating surface by a compressed spring. Application of increased pressure in the fluid being transmitted by the valve can override the spring, opening the valve. Application of control air pressure to a diaphragm connected to the rubber seating member can override the increased fluid pressure, and reclose the valve. However, this type of prior art valve does not exhibit various useful features of the spray valve disclosed herein by applicants, as described in detail hereinbelow.
Pressure controlled valves utilizing springs and diaphraghms are also disclosed in the patents of London (U.S. Pat. No. 998,019), Mintz (U.S. Pat. No. 1,035,803), Till (U.S. Pat. No. 1,779,056), Nelson (U.S. Pat. No. 1,861,506) and Welch (U.S. Pat. No. 3,038,488). However, the valves disclosed in these patents differ in one or more material respects from the valve disclosed hereinbelow. The valve in the patent of London has a spring but does not have a diaphragm, and is of a completely different geometry from the valve disclosed by applicants. The Mintz patent discloses a valve of a more complex form containing a porous medium for filtration of air (see FIG. 1, No. 23; Page 1, lines 60-64). The valve disclosed in the Till patent operates through rupture of a diaphragm which must then be replaced, unlike applicants' valve (See p. 1, lines 11-21; p. 3, lines 37-78). The patents of Nelson and Welch disclose valves of greater complexity and considerably different geometry from the valve disclosed by applicants hereinbelow.